Signaling system



-Nov. 17, 1942. c.' w. HALLIGAN x 2,302,544

SIGNALING SYSTEM /NVE/v TOR C. W HALL/GAN ATTORNEY lNov. 17, 14942. c. w.HA-1.|.|GN. 2,302,544

S'IGNALING spi-STEM /A/VENTOR C. W HA LL/GAN l Patented Nov. 17, 1942 SIGNALING SYSTEM Clair W. Halligan, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application May 10, 1939, Serial No. 272,738

11 Claims.

This invention relates to electric signaling and.

particularly to signaling devices for use in telephone systems.

The objects of the invention are to increase the effectiveness of signaling over telephone lines;

Cil

to utilize the signaling current for operating both.

visual and audible signal devices at a subscribers station; to postpone the actuation of one of the signals under the control of a delay mechanism operated by the signaling current flowing in the line; and in other respects to secure improvements in signaling systems and devices.

These objects are realized by means of a signaling system in which a communication line, such as a telephone subscribers line, is provided at the substation with a visual signal, an audible signal, and a time measuring mechanism; in which the presence of signaling current in the line energizes the visual signal to attract the subscribers attention; in which the signaling current flowing in the line is also utilized by the ,Y

timing mechanism to measure a predetermined interval following the commencement of the signaling operation; and in which the timing mechanism, having measured said interval, renders the audible signal eective to respond thereafter; j;

to the signaling current to attract the subscribers attention more positively in case he fails to recognize the visual signal.

A feature of the invention is a system of this character in which the delay interval preceding?.

a tube at the expiration of the interval, and ini which the tube, when ionized, serves to close the operating circuit for the audible signal.

Another feature is a signaling system in which alternating signaling current is applied to the l line to operate rst the visual signal and then, after the delay interval, the audible signal, and in which a gas-lled discharge tube serves to rectify the signaling current and supply it to the timing mechanism for measuring the delay interval.

According to a further feature the gas-iilled tube, which supplies the rectied signaling current to operate the time measuring mechanism, glows during the delay interval as a visual signal to the subscriber that his line is `r-eing called.

The foregoing and other features of the invention will be described in the detailedl specication.

In the drawings accompanying the specieation:

Fig. l shows one form of the signaling system applied to subscribers lines in a manual telephone exchange; and

Fig. 2 shows another form of the signaling system applied to subscribers lines in an automatic telephone exchange.

In the system illustrated in Fig. 1 the subscribers line, which appears in a jack |0| at an cperators position in the central oice, is provided at the substation with a visual signal |02 for attracting the called subscribers attention, in case he is near his telephone, when his line is first called by the operator at the central cnice. The signal |02 may be of any suitable type, such as a gas-filled lamp which ionizes and glows in response to the application of ringing current to the line.

The line |00 is also equipped at the substation with the usual audible ringer |03 which, however, is so arranged that it does not respond until the ringing current has persisted in the subscribers line for a predetermined interval of time. This interval of time is measured by a delay mechanism which includes a time measuring condenser |04, a charging resistance |05 over which said condenser is charged, and a three-electrode gasfilled tube |05. The current for charging the time measuring condenser |04 is derived by means of a tube |01 which rectifies the incoming alternating ringing current. The rectied current is applied to the condenser |04 through resistance |05 and also is stored in a condenser I 08 from whence it is drawn to charge and to maintain charged the time measuring condenser |04. In order to charge condenser |08 to a voltage high enough to operate tube I 00, a transformerv |09 is employed.

The subscribers station is further equipped with the usual telephone transmitter III), receiver I I, and the associated induction coil and switchhook contacts.

In the modication shown in Fig. 2 the subscribers line 200 appears in the terminals of automatic switches in the central office. At the substation this line is also equipped with the visual signal lamp 20|, the audible ringer 202 and with the time delay mechanism comprising the time measuring condenser 203, charging resistance 204 and the gas-filled tube 205. The means for obtaining the charging current for the condenser 203, is, however,` somewhat different. This means comprises a polarized relay 206 connected across the subscribers line in series with a condenser 201. For each operation of the relay 206 on alternating half-cycles of the ringing current a circuit is closed for condenser 203 through resistances 209 and 204 and for the storage condenser 208 through the resistance 20S.

To insure suicient voltage for operating the lamp 20| and the time delay mechanism a transformer 2I0 may be inserted in the line as illustrated. If, however, the ringing current is of suiiicient voltage, this transformer may be omitted.

A detailed description of the signaling system will now be given, iirst discussing Fig. l and then Fig. 2.

Assume that the subscriber of a line 2 wishes to converse with the subscriber of line |00, which is equipped with the visual and audible signals. The operator in the central office answers the calling subscriber in the usual manner by inserting her answering plug H3 in the Vjack |44 of the calling line and learns that a called line is desired. Thereupon she seizes the calling plug ||5 of her cord circuit and inserts it in the jack |0| ci the called line. This results in the operation of sleeve relay ||6 in a circuit from battery through the winding of said relay, over the sleeve of the plug and jack, to ground through the winding of cut-off relay |1. Next the operator closes her ringing key I8 to initiate the ringing operation. The closed ringing key H8 completes a circuit from Vbattery through its contacts and the winding of relay ||9 to ground at the normal contacts of relay |20. Relay ||0 locks in a circuit from battery through they contacts of relay H6, contacts and winding of relay ||0 to groundl at the normal contacts of relay |20. Relay ||9 also closes the ringing circuit for supplying ringing current from alternating current source |2| to the called line |00.

The ringing circuit is opened and closed periodically by the interrupter |22 and may be traced from generator 2|, battery |23, through conducting segments of interrupter |22, winding of relay |20, 'inner lower front contacts of relay H9, ring of the plug ||5 and jack |0|, thence over the ring conductor |24 of the line to the substation, where it flows through the resistance |25 and the glow tube |02 and in parallel therewith through the condenser |26 and the primary winding of transformer |09, to the tip conductor E21 of the line, returning through the tip of the jack and plug to ground at the upper front contact of relay H0. Current iiowing in these circuits lights the glow lamp |02 and energizes the transformer |09. and does not respond at this time to the current flowing over the circuits traced.

The lamp |02 serves as a visual signal to give the subscriber immediate notice that his line is being called. If he is near his telephone and sees the lighted lamp, he responds by removing his receiver, and ringing current at the central oiiice is tripped in the usual manner, which will be described hereinafter. If, however, the subscriber is not in the immediate vicinity of his telephone or does not notice the glowing lamp, the central office mechanism will continue to apply ringing current to the line, energizing the primary winding of the transformer |00 and inducing a corresponding voltage across the sec-rondary winding of the transformer. The voltage across the secondary winding of the transformer is applied, through resistances |28 and |29 and condenser |08, across the control elec-V trodes |30 and |3| ofthe tube |01. This voltage ionizes the control gap, whereupon the main gap is also ionized. Since the main gap of the tube Relay |20, however, is marginal during each ringing interval by current supplied bell |03 ceases to ring.

conducts in only one direction, current flows,

, said upper terminal is postive) through the resistance |28, anode |32 of the tube, cathode |3| thence in parallel through the storage condenser |08 and through the resistance |05 and condenser |04 to conductor |24 and returning to the lower terminal of the secondary winding of the transformer 09. The time measuring condenser |04 accumulates a charge at a rate depending upon the value of the resistance |05, and the storage condenser |08 accumulates a charge for purposes to be explained hereinafter.

Assuming, as above suggested, that the subscriber does not observe the glow lamp |02 and that he fails to answer the call within a predetermined interval of time, the condenser |04 will accumulate a charge sufcient to ionize the control gap of the gas-filled tube |00, the condenser being connected across this gap through the resistance |34. Ionization of the control gap of tube |00 causes a discharge across the main gap. Since the main gap is in series with the ringer |03, the ringer now responds to ringing current incoming over the line. The circuit for the application of ringing current to the bell |03 may be traced from conductor |21, during each half cycle that the positive pole of the generator |2| is connected to this conductor, through the ringer |03, anode |35 and cathode |36 of tube |06, conductor |24 and thence through the trip relay 20,

interrupter E22, battery |23 to the opposite pole of generator |2|, which is negative Since no current flows across the main discharge gap of the tube |06 on the alternate half cycles of the ringing current, namely, when the conductor |24 is positive and the conductor |2| negative, it is necessary to maintain the control gap of the tube ionized throughout the ringing interval of the interruptor |22. This is accomplished by making the resistance |34 suiiiciently high to limit the amount of current drawn from the condenser |04 and by providing the storage condenser |08. By limiting the amount of current taken from the condenser |04 it is possible for the condenser |03, which may be of relatively large capacity ii" desirable, to replenish the condenser |04 at a rate suiiicient to prevent the charge on condenser |04 from falling below the sustaining voltage of the control gap of the tube |00. The charge on the storage condenser |08 is also replenished from the rectifier |01. When the interruptor |22 reaches the silent interval segment, the generator |2| is disconnected from the line, and the Upon the reclosure of the ringing circuit by the interrupter |22, the bell begins to ring immediately, without waiting for any delay interval, since the condenser |08 may be made suiiiciently large in capacity to maintain the condenser |04 charged throughout the silent interval of the interrupter |22.

This procedure continues until the called party removes his receiver or until the call is abandoned. The removal of receiver from the switchhook closes the usual low resistance bridge across the line conductors |24 and |21, and the marginal tripping relay |20 now operates to disconnect the ringing machine automatically. If the called party answers during a ringing interval, the relay |20 is operated by current from the generator |2| and battery |23; if he answers during the silent interval current for operating the relay |20 is supplied from the battery |31 over interrupter |30, which is driven in synchronism with interruptor |22. Relay |20 in operating releases relay l0, and the latter relay disconnects the ringing machine from the line and closes the tip and ring conductors of the cord circuit for conversation. The lamp |02 is now extinguished, and the bell |03 ceases to ring. Furthermore, the removal of the receiver by the called party serves to discharge the condensers |04 and |08 in order that the time measuring mechanism may be restored to its normal condition ready for the next use. The discharge circuit for these condensers may be traced from conductor |24, which is connected to one terminal of each of the condensers, through contacts |39 of the switchhook, conductor |40, to the other terminal of condenser |04 and through resistance |05 to the other terminal of condenser |08.

When the subscribers have iinished conversing the operator removes the cord circuit, and the equipment is restored to its normal condition.

Since the rectier tube |01 glows during the time that signalling current is applied to th-e subscribers line7 this tube, in addition to its reotifying function for charging the condensers, may serve as a visual signal to notify the subscriber that his line is being signaled. In such a case it would not be necessary to provide the separate signal tube |02.

Referring now to the modication disclosed in Fig. 2, assume that the subscriber of line 2II in a dial oice wishes to converse with the subscriber of line 200, the latter being equipped with both visible and audible signals. The calling subscriber initiates the call in the usual manner and operates his dial 2|2 to extend his line by way of automatic switches, including the selector switch' S and connector swith C, to the called line 200.

When the connector C has been set on the terminals of the called line 200 and has found the line to be idle, relay 2 I3 operates in the wellknown manner and locks over its upper winding and contact to the sleeve conductor 2M, which is grounded at this time. Relay 2|3 closes the ringing circuit, which may be traced from the generator 2I5 through battery ZIE, interrupter 2|`|, lower contacts of relay 2|3 through the.

lower winding and lowermost back contact of the tripping relay 2| 0, inner lower front contact of relay 2|3 over a brush of connector switch C to conductor 2 I9, thence through the primary winding of transformer 2|0 and condenser 220 and ,l

returning over the line conductor 22| through the connector C, uppermost contact of relay 2|3 to ground at the uppermost back contact of relay 2 I8. During the ringing interval of interrupter 2I'| alternating ringing current from the source 2|5 flows through the primary winding of the transformer 2|0 and induces a corresponding voltage across the secondary winding thereof. This voltage across the secondary winding causes current to flow through the lamp 20| and resistance 222, and the lamp glows as a visual signal to the subscriber.

The alternating voltage induced across the secondary winding of the transformer also causes an alternating current to flow in the circuit including the polarized relay 200 and condenser 201. Since relay 206 is polarized, it responds only to the alternate half cycles of the current, serving as a rectifier for charging the time measuring condenser 203 and the storage condenser 208. The charging circuit may be traced from conductor 223, through the contact of relay 200, closed only on half cycles of like polarity, through resistance 209 and storage condenser 208 to conductor 224 and in parallel therewith through the resistance 204 and the time measuring condenser 203. Condenser 203 charges at a rate depending on the value of resistance 204 to measure a predetermined interval of time, and condenser 208 assumes a storage charge. At the end of the measured interval, when condenser 203 reaches the ionizing voltage of tube 205, the tube discharges, and a circuit is closed for applying the alternating ringing current to the bell 202. The circuit for operating the bell may be traced from conductor 223, ringer 202, anode 225, cathode 220 tolconductor 224. During each half cycle that conductor 223 is positive, current ows over this circuit, and the ringer 202 operates as an audible signal to the called party. During the non-conducting half cycles of the tube 205 and during the silent intervals of the interrupter 2|1 the condenser 203 is assisted by the storage condenser 203 in maintaining its charge up to the ionizing potential of the control gap of the tube.

When the called party answers by removing his receiver 221 from the switchhook, increased current flowing through the relay 2|3 causes the relay to operate and lock over its upper winding and contact to the grounded conductor 2|4. Relay 2|8 also removes the ringing current and closes the tip and ring conductors through for conversation. At 'the called station the closure of contacts 228 completes a discharge circuit for condensers 203 and 208 to restore the time measuring device to its normal condition.

When the subscribers nish conversation and replace their receivers, theautomatic switches are' released, and all equipment is restored to normal.

Should the subscriber wish to have his bell operate immediately that ringing current is applied to his line he may disable the time measuring mechanism by operating a key or suitable manual switch. In Fig. 1, for example, closure of the switch I 4| places the control gap of the tube |06 across the conductors |24 and |21 in series with a resistance |42. With this circuit closed the application of ringing current to the line causes the immediate inonization of the tube and the immediate ringing of the bell |03. Similarly in Fig. 2 the subscriber may disable the time delay mechanism by closing the switch 220.

Numerous variations and modifications of these systems willalso be apparent to those skilled in the art. For example, the transformers may be omitted, provided the voltages applied at the central ofce are sufficiently high to operate the equipment at the substation. Also it may be desirable to connect the ringers to ground, instead of bridging them across the line, at substations equipped with impulse dials.

What is claimed is:

I l. The combination in a telephone system of a "j line having a station thereon, a source of signaling` current, means for connecting said source to the line, a lamp at said station energized by the signaling current flowing in said line, -a ringer at said station, a time measuring condenser at said station, a charging circuit including a resisto-r for charging said condenser at a definite rate with the signaling current received over said line, and means responsive to the charge accumulated on said condenser at the end of a predetermined interval for rendering said ringer responsive to the signaling current flowing in said line.

2. The combination in a telephone system of a subsoribers line having a station thereon, a source of alternating current, means for connecting said source tothe line, a lamp at said station energized by the current iiowing in said line to give a visual signal, a bell at said station, means at said station for rectifying the alternating current flowing in said line, timing means operated by said rectified current for measuring an interval of time, and means controlled by said timing means for rendering said bell responsive after the expiration of said interval to the alternating current fio-wing in said line.

3. rIhe combination in a telephone system of a subscribers line having a station thereon, a source of alternating current, means for connecting said source to the line, a lamp at said station energized by the current flowing in said line to give a visual signal, an audible device at said station, means at said station for rectifying the alternating current in said line, a timing condenser charged at a definite rate by said rectied current to measure a desired interval of time,

and means controlled by the charge on said condenser upon the completion of the measured interval for rendering said audible device responsive thereafter to the alternating current flowing in said line.

4:. The combination in a telephone system of a subscribers line having a station thereon, a source of alternating current, means for connecting said source to the line, a lamp at said station energized by the current flowing in said line to give a visual signal, an audible device at said station, means at said station for rectifying the alternating current in said line, a timing condenser charged at a definite rate by said rectified current to measure a desired interval of time, a discharge tube ionized by the charge on said condenser at the end of the measured interval, and a circuit rendered effective by the ionization of said tube for connecting said audible device to said line to respond thereafter to the alternating current flowing therein.

The combination in a telephone system of a subscribers line having a station thereon, a source of signaling current, means for connecting said source to said line, a visual device at said station energized by the signaling current iowing in said line, an audible device at said station, a time measuring condenser at said station charged at a given rate by the signaling current iiowing in said line, means responsive to the charge accumulated on said condenser at the end of a measured interval for rendering said audible device responsive to the signaling current in said line, a storage condenser charged by the signaling current, and means for supplying the charge on said storage condenser to the time measuring condenser.

6. The combination in a telephone system of a subscribers line having a station thereon, Pa source of alternating current, means for connecting said source to the line, a lamp at said station energized by the current flowing in said line to give a visual signal, an audible device at said station, means at said station for rectifying the alternating current in said line, a timing condenser charged at a deiinite rate by said rectified current to measure a desired interval of time, means controlled by the charge on said condenser upon the completion of the measured interval for rendering said audible device responsive thereafter to the alternating current flowing in said line, and means controlled by the subscriber in answering a call for discharging said condenser.

7. In a telephone system, a subscribers line, a source oi alternating signaling current, means for connecting said source to the line, a ringer at the substation oi said line, a time measuring mechanism for rendering said ringer responsive to said signaling current after a measured interval following the connection of said source to the line, and a gas-filled tube at said substation responsive to the signaling current to emit a glow as a, calling signal and to supply rectiiied current for the operation of said time measuring mechanism.

8. The combination in a telephone system of a subscribers line having a station thereon, a source of signaling current, means for connecting said source to the line, a visual signal at said station energized by the current flowing in said line, an audible signal at said station, a timing condenser charged at a denite rate by the signaling current flowing in said line to measure a desired interval of time, a discharge tube ionized by the charge on said condenser at the end of the measured interval, a circuit rendered eiective by the ionization of said tube for rendering said audible signal responsive to the signaling current iiowing in said line, and a storage condenser charged by the signaling current in said line and serving to charge said timing condenser.

9. The combination in a telephone system of a telephone line having a station thereon, a source of signaling current, means for connecting said source to the line intermittently, a visual signal at said substation energized by the signaling current flowing over said line, an audible signal at said station, a timing condenser charged at a delinite rate by the signaling current for measuring a desired interval of time, a discharge tube ionized by the charge on said condenser at the end of the measured interval, circuit means controlled by said discharge tube for rendering said audible signal responsive to the signaling current flowing over said line, and a storage condenser charged by the signaling current in said line and serving to replenish the charge on said timing condenser during the intervals when no signal current is ilowing in said line.

10. The combination in a telephone system of a subscribers line having a station thereon, a source of signaling current, means for connecting said source to sai-d line, a visual device at said station energized by the signaling current flowing in said line, an audible device at said station, a time measuring condenser charged at a given rate by the signaling current flowing in said line, means responsive to the charge on said condenser at the end of the measured interval for rendering said audible device responsive to the signaling current in said line, a storage condenser charged by the signaling current and serving to transfer its charge to the time measuring condenser, and means controlled by the subscriber in answering said signal devices for automatically discharging both of said condensers.

11. In a telephone system, a subscribers line, a source of alternating signaling current, means for connecting said source to the line, an audible signal at the substation of said line, a condenser at said substation for measuring a predetermined interval of time following the .connection of said source to the line, a gas-filled tube at said substation responsive to said alternating signaling current to emit a glow as a calling signal and to supply rectified current for charging said time measuring condenser, and means controlled by the charge on said condenser at the end of the measured interval for rendering said audible signal responsive to the signaling current flowing in said line.

CLAIR W. HALLIGAN. 

